Brent Christensen's Ice Castles could be the haven for an ice queen or the hideout for a race of wintery sprites. But they're actually man-made structures, created by pouring water over an icicle structure. The results are towering architectural sculptures that seem plucked from a place of myth and legend and plopped down in Minnesota and Colorado.

After building the structures with icicles, the Ice Castles team turns on sprinklers in freezing temperatures, letting the castles grow over the base. Some of the structures have tunnels, allowing visitors to step inside an otherworldly realm of ice. At night, the structures are lit up, adding an extra touch of the unnatural to these forms.